1. Field of the Invention
The present invention relates to a system for automatically tuning a receiver for a DVB-T (Digital Video Broadcasting-Terrestrial) system.
The use of digital broadcasting is currently growing in popularity throughout the world, as it offers a wide choice of channels and superior video and audio quality compared to that of analogue signal broadcasting.
In the case where the DVB-T receiver of a digital broadcasting system is mobile, it is necessary to ensure that the receiver has constant access to the highest quality signal available for the particular service required. In most of continental Europe, for example, a DVB-T transmission system known as “Single Frequency Network” (SFN) transmission is adopted, in this system a user travelling between different areas does not have to re-tune the frequency of the service required, as this is the same for all areas even if they are covered by different transmitters. By contrast, countries such as the United Kingdom apply a transmission system known as “Multi Frequency Network” (MFN) transmission, and with this system the user has to re-tune the receiver during the journey in order to continue to receive the optimum signal quality available.
Re-tuning in this way is necessary with the MFN transmission system, as the total area for which the service is available is split into “area-cells”, each of which constitutes the area covered by one DVB-T transmitter A number of DVB-T transmitters are therefore used to transmit a service to various different areas defined by the area-cells
Previous MFN transmission systems therefore present a problem, in that a user moving from one area-cell to another must re-tune the DVB-T receiver to a new frequency in order to continue to receive the same service, as the transmission frequency of the service varies from one area-cell to another. This re-tuning is inconvenient and can be difficult to achieve.